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<div class="section boost_icl_implementation_inplace_and_infix_operators" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_icl.implementation.inplace_and_infix_operators"></a><a class="link" href="inplace_and_infix_operators.html" title="Inplace and infix operators">Inplace
      and infix operators</a>
</h3></div></div></div>
<p>
        For the major operations <span class="emphasis"><em>addition, subtraction, intersection</em></span>
        of <span class="bold"><strong>icl</strong></span> containers and for <span class="emphasis"><em>symmetric
        difference</em></span> inplace <code class="computeroutput"><span class="keyword">operator</span></code>s
        <code class="computeroutput"><span class="special">+=</span> <span class="special">|=,</span>
        <span class="special">-=,</span> <span class="special">&amp;=</span></code>
        and <code class="computeroutput"><span class="special">^=</span></code> are provided.
      </p>
<p>
        For every <span class="emphasis"><em><span class="bold"><strong>inplace</strong></span></em></span> operator
        
</p>
<pre class="programlisting"><span class="identifier">T</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="identifier">o</span><span class="special">=</span> <span class="special">(</span><span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">object</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">P</span><span class="special">&amp;</span> <span class="identifier">operand</span><span class="special">)</span>
</pre>
<p>
        the <span class="bold"><strong>icl</strong></span> provides corresponding <span class="emphasis"><em><span class="bold"><strong>infix</strong></span></em></span> operators. 
</p>
<pre class="programlisting"><span class="identifier">T</span> <span class="keyword">operator</span> <span class="identifier">o</span> <span class="special">(</span><span class="identifier">T</span> <span class="identifier">object</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">P</span><span class="special">&amp;</span> <span class="identifier">operand</span><span class="special">){</span> <span class="keyword">return</span> <span class="identifier">object</span> <span class="identifier">o</span><span class="special">=</span> <span class="identifier">operand</span><span class="special">;</span> <span class="special">}</span>
<span class="identifier">T</span> <span class="keyword">operator</span> <span class="identifier">o</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">P</span><span class="special">&amp;</span> <span class="identifier">operand</span><span class="special">,</span> <span class="identifier">T</span> <span class="identifier">object</span><span class="special">){</span> <span class="keyword">return</span> <span class="identifier">object</span> <span class="identifier">o</span><span class="special">=</span> <span class="identifier">operand</span><span class="special">;</span> <span class="special">}</span>
</pre>
<p>
      </p>
<p>
        From this implementation of the infix <code class="computeroutput"><span class="keyword">operator</span>
        <span class="identifier">o</span></code> the compiler will hopefully use
        return value optimization <a href="http://en.wikipedia.org/wiki/Return_value_optimization" target="_top">(RVO)</a>
        creating no temporary object and performing one copy of the first argument
        <code class="computeroutput"><span class="identifier">object</span></code>.
      </p>
<div class="caution"><table border="0" summary="Caution">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../../../../doc/src/images/caution.png"></td>
<th align="left">Caution</th>
</tr>
<tr><td align="left" valign="top"><p>
          Compared to the <span class="emphasis"><em>inplace</em></span> <code class="computeroutput"><span class="keyword">operator</span>
          <span class="identifier">o</span><span class="special">=</span></code>
          every use of an <span class="emphasis"><em>infix</em></span> <code class="computeroutput"><span class="keyword">operator</span>
          <span class="identifier">o</span></code> requires <span class="emphasis"><em><span class="bold"><strong>one extra copy</strong></span></em></span> of the first argument
          <code class="computeroutput"><span class="identifier">object</span></code> that passes a container.
        </p></td></tr>
</table></div>
<p>
        Use infix operators only, if
      </p>
<div class="itemizedlist"><ul type="disc">
<li>
          efficiency is not crucial, e.g. the containers copied are small.
        </li>
<li>
          a concise and short notation is more important than efficiency in your
          context.
        </li>
<li>
          you need the result of operator <code class="computeroutput"><span class="identifier">o</span><span class="special">=</span></code> as a copy anyway.
        </li>
</ul></div>
<a name="boost_icl.implementation.inplace_and_infix_operators.time_complexity_of_infix__code__phrase_role__identifier__operators__phrase___phrase_role__identifier__o__phrase___code_"></a><h6>
<a name="id1133408"></a>
        <a class="link" href="inplace_and_infix_operators.html#boost_icl.implementation.inplace_and_infix_operators.time_complexity_of_infix__code__phrase_role__identifier__operators__phrase___phrase_role__identifier__o__phrase___code_">Time
        Complexity of infix <code class="computeroutput"><span class="identifier">operators</span> <span class="identifier">o</span></code></a>
      </h6>
<p>
        The time complexity of all infix operators of the <span class="bold"><strong>icl</strong></span>
        is biased by the extra copy of the <code class="computeroutput"><span class="identifier">object</span></code>
        argument. So all infix <code class="computeroutput"><span class="identifier">operators</span>
        <span class="identifier">o</span></code> are at least <span class="emphasis"><em>linear</em></span>
        in <code class="computeroutput"><span class="identifier">n</span> <span class="special">=</span>
        <span class="identifier">object</span><span class="special">.</span><span class="identifier">iterative_size</span><span class="special">()</span></code>.
        Taking this into account, the complexities of all infix operators can be
        determined from the corresponding inplace <code class="computeroutput"><span class="identifier">operators</span>
        <span class="identifier">o</span><span class="special">=</span></code>
        they depend on.
      </p>
</div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2007 -2010 Joachim Faulhaber<br>Copyright &#169; 1999 -2006 Cortex Software GmbH<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
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